1. Field of the Invention
The present invention relates to an optoelectronic transceiver, or transmitting and receiving unit, as generically defined by the preamble to claim 1, which is suitable in particular for bidirectional data transmission by means of optical waveguides.
2. Description of the Related Art
For bidirectional data transmission via optical waveguides, optoelectronic transmitting units and receiving units or so-called transceivers are necessary on the various ends of the optical waveguides. One possibility for designing such transceivers is known for instance from European Patent Disclosure EP 0 410 143 A2. This reference provides that an optoelectronic transmitting unit and an optoelectronic receiving unit are disposed at an angle of 90° to one another. Via a suitable tee coupler or beam splitter element, it is assured that the radiation emitted by the transmitting unit is injected into an optical waveguide, and the radiation coming from the optical waveguide is deflected in the direction of the receiving unit. Such transceivers, however, require great effort and expense for exact adjustment or disposition of the two transmission and receiving units relative to the tee coupler and the optical waveguide. Furthermore, this arrangement always requires a suitable tee coupler; in other words, the number of components required is high.
In Japanese Patent Disclosure JP 8-179169, it is therefore provided that the transmitting unit and the receiving unit are disposed along a common optical axis, and this axis is identical to the optical axis of the optical waveguide. The receiving unit here is disposed adjacent to the exit face of the optical waveguide; behind or facing away from the optical waveguide, the transmitting unit follows. The tee coupler of the kind required in the arrangement in the above-cited reference, for instance, thus becomes unnecessary. The radiation emitted by the transmitting unit is injected into an SiO2 waveguide layer on a supporting substrate, carried past the receiving unit, and injected into the optical waveguide from the waveguide layer. The reference also proposes tuning the reception and transmission wavelengths of the two units to one another. Thus the corresponding transmitting unit emits at a wavelength at which the respective receiving unit does not respond. A problem with such an arrangement is the requisite high expense in production terms, since first the waveguide layer must be applied to the semiconductor supporting substrate, and then the semiconductor stack of transmitting units and receiving units must be applied over that. Hence complicated semiconductor production techniques are required to manufacture this component. Furthermore, in the proposed arrangement, problems arise when the radiation emitted by the transmitting unit is injected into the waveguide layer and from there into the optical waveguide. Injection losses at these locations can hardly be avoided, and thus the overall efficiency of this arrangement suffers in turn. It should also be noted that the respective active layer regions of the two semiconductor components are oriented relative to the optical axis in such a way that the optical axis is located in the plane of each of the active regions, or is oriented parallel to that. Depending on the manner of imposition on this element of the radiation that leaves the exit face of the optical waveguide, additional problems arise. For instance, in the case of direct irradiation of this element via the optical waveguide, adjustment problems arise. Then a relatively narrow surface area of the receiving element must be oriented as highly exactly as possible relative to the extraction end of the optical waveguide, which requires corresponding effort and expense in the assembly process. Conversely, if provision is made for imposition by injecting the radiation of the optical waveguide into the waveguide layer, then once again the losses and problems already discussed above occur upon injecting and extracting this radiation.